Inhalers are commonly used to deliver various medicaments to users via the user's nose or mouth. Such medicaments increasingly include dry powders. A number of considerations affecting the efficacy of delivery may be presented, particularly in the case of dry powders. For example, it may be important to ensure that the appropriate dose is metered and expressed, that the medicament is properly dispersed in the conveying fluid (e.g., the carrier gas), that the delivery device is not unduly susceptible to user error in operation, and/or that undue inhalation strength is not required. Further considerations may include the operating complexity, portability and size of the delivery device. Because inhalation therapy often requires numerous applications, the cost of providing the dosage may be of particular importance.